Electronic devices (cellular telephones, wireless modems, computers, digital music players, Global Positioning System units, Personal Digital Assistants, gaming devices, etc.) have become a part of everyday life. Small computing devices are now placed in everything from automobiles to housing locks. The complexity of electronic devices has increased dramatically in the last few years. For example, many electronic devices have one or more processors that help control the device, as well as a number of digital circuits to support the processor and other parts of the device.
Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, data and so on. These systems may be multiple-access systems capable of supporting simultaneous communication of multiple wireless communication devices with one or more base stations.
Mobile devices may include a variety of circuits used during operation. For example, an oscillator may be used to synchronize various circuits across a board or integrated circuit within a mobile device. Furthermore, different circuits within a mobile device may operate using different frequencies. Therefore, mobile devices may generate multiple reference signals for different purposes.
Frequency synthesizer circuits may use capacitors for a variety of reasons. However, capacitors may require a relatively large area when implemented as integrated circuit. Therefore, it may be beneficial to reduce the area of capacitors where possible. A Miller capacitor multiplier is described in “Adaptive Miller capacitor multiplier for compact on-chip PLL filter” by Tang, Y., Ismail, M., and Bibyk, S. in Electronics Letters, 2003, 39, (1), pp. 43-45. A loop capacitance multiplier is described in “A 2.4-GHz monolithic fractional-N frequency synthesizer with robust phase-switching prescaler and loop capacitance multiplier” by Shu, K., Sanchez-Sinencio, E., Silva-Martinez, J., and Embabi, S. in IEEE Journal of Solid-State Circuits, 2003, 38, (6), pp. 866-874.